What is the critical angle for a ray trying to pass from ice (n = 1.31) into air?
(Unit=deg)

49.8°

Explanation:

Data obtained from the question include:

n (refractive index) = 1.31

C (critical angle) =?

The refractive index and the critical angle are related by the following equation:

n = 1/sineC

Now, using the above equation, we can easily find the value of the critical angle as show below:

n = 1/sineC

1.31 = 1/sineC

Cross multiply to express in linear form as shown below:

1.31 x sineC = 1

Divide both side by 1.31

sineC = 1/1.31

sineC = 0.7634

Take the inverse of sine of both side

C = sine^-1 (0.7634)

C = 49.8°

Therefore, the critical angle is 49.8°